* there can be more than 1 active period. This has been added to deal with temporary budgets (like "10000€ to spent in the next 3 months")
* all active budgets are retrieved
* budget available for everyone now displayed correctly
also :
* fixing some hardcoded values
* removing a warn
* budget period management
* budget management (budgets lines are defined for a given budget period)
budget_owner_search is the popup to select a librarian as budget owner